This invention relates generally to means for preserving beaches, and limiting beach erosion and replenishing beach sand, and more particularly to a beach erosion reversal system and method.
During periods of high winds and waves, particularly during winter months and periods of storms coupled with high tides, the waves which break upon beaches are referred to as destructive waves. These destructive waves crest resulting in repeated periods of strong undertow or wave recirculation out to sea which act upon the beach sand carrying it away from the beach in a conveyor belt-like action that pulls the sand into the ocean. The most extensive research has shown that, on an average, the United States' coastlines are being eroded at the rate of 30 centimeters per year.
During periods when winds are calm, waves do not crest and the substantially smaller circulation within each wave allows this conveyor belt-type action to work constructively, carrying sand up onto the beach for deposit there. These waves are known as constructive waves which act to rebuild the beach area.
Because of the increasing presence of sea walls, groins, and buildings which have been constructed ever closer to beach areas, this conveyor belt-like action of the constructive summer waves has been substantially blocked. Indeed, destructive winter waves are successfully stopped from reaching buildings. However, these sea walls also stop the constructive summer or gentle wave action as well. The sea wall not only stops the constructive waves but it also spreads the sand which has been collected within constructive waves throughout the water. Thereafter, the sand is simply returned to the sea having been thwarted in its beach healing effort. Thus, all waves approaching such developed beach areas result in some form of destruction or beach erosion because the normal wave action of otherwise constructive waves is interrupted by these near-beach structures.
Perhaps the only effective way which modern man has found to cope with this beach erosion problem is to simply redeposit masses of sand onto the beach after nature has done its destructive work.
Researchers in the field of beach erosion and preservation have determined that the most productive process apparently available is "beach renourishment", i.e. the hauling of new sand onto the beach. This process, however, enables destructive waves to pull even larger amounts of loose material, as well as much of the new sand, away from the beach. Thus, the productive and expensive benefits of this beach renourishment could be washed away in a short period of time and typically are.
Of course, a major drawback of this regeneration or renourishment process for beaches is the massiveness of the cost of either trucking in sand from inland, or using massive dredges to deposit fresh sand atop the eroded beach area. Another major short fall of this renourishment process lies in the available timing for placement of this new sand atop these beaches. Summer waves that build the beaches require this gentle flow pattern in order to remain constructive. If renourishment is performed in the summer, these waves will be interrupted, thus causing erosion on the original sand and undermining the renourished sand. Further, the techniques now available for spreading sand with earth movers typically result in the formation of a ledge at the far reach of these earth movers. This sudden drop forming the ledge acts as a temporary seawall itself, blocking both constructive and destructive waves. The original sand is undermined preparing the beach for drastic erosion during the next destructive wave period.
The present invention is intended to provide a full scale structural system and method which may be deposited and used along an eroded beach reversing much of the effects of erosion by constructively altering the flow of water in destructive waves. The structures are fabricated of economical materials which are designed to themselves be eroded away by the wave action so as not to result in beach clutter avoiding a "next generation" problem in and of themselves.